This is fucking bullshit, I just bought 3 used games and because they are related to steam, they were invalid... I have a solution for that if they think they are cool and funny, and simply money hungry. My solution was going to my local frys, opening each new game that I bought used and taking the instruction manual and simply entering that product key code into my steam account and woolah!!! a free game and if I am caught I just say I wanteed the manual, who would take you to court for that unless they actually knew what you were doing, pass this on because I did it for fear2, half life 2 episode 1 and 2, etc. so I dont really need to buy games anymore just get instruction manuals to get the game free electronically!!!